JPS62187116A - Production of pzt type piezoelectric ceramic powder sinterable at low temperature - Google Patents

Abstract

PURPOSE:To produce high density powdery starting material sinterable at low temp. and having superior electrical characteristics by forming a composite precipitate of Zr and Ti compounds, washing the precipitate, further precipitating a Pb compound in a composite state, washing the resulting composite precipitate and calcining it. CONSTITUTION:An aqueous soln. of a Zr compound is dropped into an aqueous ammonia soln. and reacted. An aqueous soln. of a Ti compound is further dropped to form a composite precipitate of Zr and Ti hydroxides. This precipitate is aged, washed and dispersed again in an aqueous ammonia soln. and an aqueous soln. of a Pb compound is dropped to form a composite precipitate of Zr, Ti and Pb hydroxides. This precipitate is separated by filtration, washed, dried, calcined at 500-1,100 deg.C and ground. By this method, powdery starting metarial suitable for the production of PZT type piezoelectric ceramics is obtd. with inexpensive materials.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention provides lead titanium zirconate (lead titanium zirconate) with low temperature sinterability and high performance.
The present invention relates to a method for producing PZT)-based piezoelectric ceramic raw material powder.

PZT ceramics are widely used as high frequency filters, ultrasonic vibrators, and resonator elements (big amplifier elements, ignition element mechanical filters, delay line conversion elements, bimorph elements, etc.).

[Prior art]

Conventionally, dry methods and wet co-precipitation methods are known as methods for producing raw material powder for PZT ceramics.

The dry method is a method in which oxide powders of the constituent components of PZT ceramics are mixed and calcined to obtain a raw material powder.
This is the most common method that has been widely adopted.

In the wet coprecipitation method, a uniform mixture of metal compounds corresponding to the constituent components of PZT ceramics is made, a precipitate forming liquid such as alkali is added to this, the mixture is co-precipitated, and the mixture is dried and calcined to obtain a raw material powder. This method uses an aqueous solution of an inorganic metal compound as a mixed solution (Material Research Bulletin).
Material Research Bull, V
ol.

17, 101-104. (1982)) and a method using an 8g solvent solution of an organometallic compound (Ceramic Bull, No. 4).
．． 591-(1984)).

[Problem that the invention seeks to solve]

In the dry method, it is difficult to obtain raw material powder with a uniform composition (and PZ
Since it is necessary to raise the calcination temperature in order to complete the T production reaction, the resulting powder particles become coarse, making it impossible to obtain a raw material powder that is sinterable at low temperatures.

In addition, with the wet coprecipitation method, it is easy to obtain powder with excellent uniformity in composition and particle size. Particles may be formed, and a raw material powder with expected low-temperature sinterability may not be obtained. In addition, in the coprecipitation method, the concentration of the precipitate forming solution at the time of addition is constant, so if each component has different properties such as solubility, one component will form a 100% precipitate, while another component will form a 100% precipitate. % precipitate may not be produced, and the desired composition may not be obtained. Furthermore,
PZT contains lead and titanium, so when producing it by coprecipitation, if cheap titanium tetrachloride is used as the titanium raw material, the chlorine ions of titanium tetrachloride will react with the lead ions, resulting in a white color. Titanium tetrachloride cannot be used because it forms a precipitate. In this case, titanium oxynitrate can be used to prevent the formation of this precipitate, but it is not practical because it is expensive.

In addition, as a wet method, there is also a method using an organometallic compound, and in this case, no harmful anions are generated, but the raw materials are expensive and it is not suitable for industrial production.

An object of the present invention is to provide a method for producing low-temperature sinterable raw material powder, which is suitable for producing PZT-based piezoelectric ceramics with high density and excellent electrical properties, in which inexpensive titanium tetrachloride can also be used as a titanium raw material. It is in.

[Means for solving problems]

In manufacturing PZT-based piezoelectric ceramic raw material powder by a wet method, the present inventors select the initial type of precipitation for each component, and gradually convert each precipitate using the precipitate particles (precursor) as a nucleus. The powder obtained by adopting a multi-stage precipitation method is a P powder with high density and excellent electrical properties.
It was discovered that the powder can be used as a raw material powder for ZT-based ceramic sintered bodies, and the present invention was completed.

In the present invention, a zirconium compound aqueous solution is mixed with an excess precipitate forming liquid to form a precipitate, and then a titanium compound aqueous solution is mixed into the precipitate forming liquid in which the precipitate is dispersed, and the titanium compound is complexed using the zirconium compound precipitate as a core. After forming a precipitate and washing the obtained composite precipitate, the composite precipitate is again dispersed in an excess precipitate forming solution, and an aqueous lead compound solution is mixed with the composite precipitate-dispersed precipitate forming solution to nucleate the composite precipitate. A method for producing a low-temperature sinterable PZT-based piezoelectric ceramic raw material powder, which is characterized by preparing a composite precipitate of all components in which a lead compound is combined, filtering and washing the composite precipitate, and then calcining it at 500 to 1100°C. It is.

In the present invention, the reaction for forming each precipitate is carried out by adding an aqueous solution of each component to a precipitate forming solution, and then aging at a temperature of 10 to 80°C for 30 minutes or more, preferably 1 to 24 hours.

The PZT-based piezoelectric ceramic raw material powder obtained by the present invention is a low-temperature sinterable powder that can be sintered at 1000 to 1220°C to obtain a PZT-based piezoelectric ceramic sintered body with high density and excellent electrical properties. It is a powder.

In the present invention, PZT-based piezoelectric ceramics is defined by the general formula pb(Zr*↑L-,) as (where x=o, L
~0.9) PZT and the above general formula Pb/
It is a general term for PZT in which the atomic ratio of (Zr+Ti) is shifted higher or lower than 1.0, and a system in which a trace amount of a metal element is added to these.

Component compounds for making an aqueous solution of PZT-based components include hydroxides, oxychlorides, carbonates, oxynitrates, sulfates, nitrates, acetates, formates, oxalates, chlorides, oxides, etc. It will be done. If these are not soluble in water, F
It is possible to make it soluble by adding L#, etc., but the cheapest ones that can be passed through the process of the present invention are zirconium oxychloride or zirconium oxynitrate, titanium tetrachloride and lead nitrate.

As the precipitate forming liquid, alkaline aqueous solutions such as ammonia, caustic alkali, soda carbonate, ammonium oxalate, amines, etc. can be used; however, they do not contain sodium or potassium, which would affect electrical properties if mixed in trace amounts, and are easily used in the calcination stage. Aqueous ammonia is preferably used because it decomposes into water and is inexpensive.

In the present invention, in addition to washing the final precipitate, intermediate precipitates are washed. In particular, when titanium tetrachloride is used as a titanium raw material, sufficient washing is performed as an intermediate wash before adding a lead compound to remove anions, especially It is necessary to remove chloride ions. Washing is usually carried out using water or aqueous ammonia and repeating repulp washing with water, but it is preferable to repeat repulping washing with water five or more times. If the intermediate cleaning is not sufficient, lead chloride, etc., which are difficult to remove in the final cleaning, will be produced, resulting in weight loss during sintering, and sinterability and electrical properties will deteriorate.

Further, in order to obtain a powder with better performance, it is preferable to perform ripening after each precipitate is formed. Aging is carried out for a long time at low temperatures and for a short time at high temperatures, and is usually aged between 10 and 8
The time is 30 minutes or more at 0°C, preferably 1 to 24 hours.

In the present invention, in order to control the sinterability and electrical properties of PZT ceramics, trace components such as Ba, C, etc.
a+ Sr+Sn+ Mn+ A1. La+Nb,
Cs, Ge+ vl yl BL Fe, Cr, Ni.

Ir, Rh, Na, Sc, In, Ga, TIJ,
Compounds of elements such as Th can be added.

[For production]

In the present invention, a multi-stage precipitation method is adopted as a method for producing a composite precipitate, and contrary to the general method of separating each precipitate into a precipitate forming solution into an aqueous solution of each compound, an aqueous solution of each compound is sequentially separated into a precipitate forming solution. , each is aged and manufactured. In particular, the zirconium compound precipitate that becomes the molasses precipitated by this method becomes uniform fine particles, and the particle size can be easily controlled. As a result, the final target calcined powder has a uniform particle size, and low-temperature sinterability is achieved.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way.

Example 1 0.1 mole of zirconium oxychloride was dissolved in 500 mI of water to make an aqueous solution, and this solution was dropped over 15 minutes into 3N ammonia water Iz which was maintained at a temperature of 60°C and stirred, and then the temperature was increased to 60°C. The reaction was aged by holding at 40°C and stirring for 1 hour. Then, add 0.1 mol of titanium tetrachloride to 5 mol of water.
The aqueous solution dissolved in 0.00ml was added dropwise to this dispersion while stirring to form a composite hydroxide precipitate of Zr and Ti, and the precipitate was aged by continuous stirring day and night at room temperature.

After filtration, the filter cake was again dispersed in dilute ammonia water and filtered (repulp washing) several times, and CI-
After sufficiently removing ions, the filter cake was redispersed in 2.4N aqueous ammonia 11, and while stirring, 0% lead nitrate was added.
．． A solution of 2 moles dissolved in 300 ml of water was added dropwise to Z.
After forming a precipitate containing the hydroxides of r, Ti, and pb, stirring was continued day and night at room temperature to ripen the reaction product. The attached No, - ions were removed by repulp washing in the same manner as above. In addition, in order to prevent the stoichiometric ratio of each component from changing due to adhesion to the filter paper due to repulp washing with water, filtration was always performed on the same filter paper.

Then, the final filter cake was dried by keeping it at a temperature of 100°C for 5 hours, and then calcined at 750°C for about 2 hours to obtain a calcined powder of PZT ceramics and Pb(0.5Zr ・0.5Ti) Oz. Ta. The obtained calcined powder was placed in a ball mill, ethanol was added thereto, the powder was ground for 48 hours, and then heated to 100°C.
The mixture was dried for 2 hours to obtain a PZT ceramic raw material powder.

(Sample Nos. 1-1 to 1-4) Example 2 PZT ceramics Pb (0.5Zr 0.5Ti) were produced using the same process as in Example 1 but omitting the aging process.
O* raw material powder was obtained. (Sample No. 2-1 to 2-4
) Comparative Example 1 0.1 mol of titanium tetrachloride and 0.1 mol of zirconium oxychloride.
1 mole and 1 j of water! Dissolved in Ti← and Zr'
An equimolar mixed aqueous solution of " was prepared. This solution was added dropwise over 30 minutes to 3N ammonia water stirred at 60°C.
The formed precipitate was filtered off. CI- adsorbed on the cake
After sufficiently washing the ions, 0.2 mol of lead nitrate was added to the
A solution dissolved in 00+wl of water was added dropwise over 10 minutes.
A complex hydroxide of Zr, Ti and PB was precipitated.

The following is the same operation as in Example 1 to prepare PZT ceramic Pb.
(0,5Zr-0,5Ti)Ox raw material powder was obtained.

(Sample No., ratio 1-1 to ratio 1-4) Comparative example 2 Commercially available (7) PbO+ Ti0z, Zr0t 117)
Pb(0,5Zr-0,5Ti)0. They were mixed in a ball mill, calcined at 800°C for about 2 hours, and ground again in a ball mill to obtain a dry raw material powder.

(Sample No., Ratio 2-1 to Ratio 2-4) Comparative Example 3 PZT ceramic Pb (
0.5Zr ・0.5Ti) (L+ raw material powder was obtained. DTG measurement of the obtained powder showed 3.7w at around 900°C.
There was a weight loss of t%, and the formation of PbCIg was observed.

(Evaluation test) (A> Characteristics of raw material powder The particle size distribution of each raw material powder obtained in Examples and Comparative Examples was measured using a centrifugal sedimentation type particle size distribution analyzer (manufactured by Shimadzu Corporation, Model 5A-CP).
Measured using

(A-1) Average particle size: D%@ The particle size 1Dso indicated by a cumulative weight percentage of 50% is shown in Table 1 as the average particle size.

(A-2) Particle size distribution; D. /　D　+.

Particle size exhibiting a cumulative weight percentage of 90%; D. , the particle size exhibiting a cumulative weight percentage of 10%; D. The value divided by; D,
.

/　D　+. is shown in Table 1 as the particle size distribution.

(A-3) Specific surface area The specific surface area of the raw material powder was measured using an automatic specific surface area measuring device (Shimadzu Micromeritics Model 2200).

(A-4) SEM Photograph 38M observation of the powders obtained in Example 1 and Comparative Example 1 was performed using JEOL JSM-T-200.

(B) Characteristics of dielectric porcelain Piezoelectric porcelain was manufactured using each of the raw material powders obtained in Examples and Comparative Examples.

Raw material powder; 1g was put into a mold with a diameter of 20 dragons, and 2Ton/
(J" pressure) to obtain a molded body. This molded body was placed in a magnesia crucible, covered, and sintered in a firing furnace to obtain piezoelectric porcelain.

For each sample, adjust the atmosphere in the magnesia crucible)
pbo *Enclose powder, 1050℃, 1100℃, 1
Firing was performed at four levels of temperature: 150°C and 1220°C.

Heg paste was baked on both sides of the obtained piezoelectric porcelain as electrodes for measuring electrical characteristics.

(B-1) Density of compacted product The dimensional density of the compacted compact was measured. The measurement results are shown in Table 1.

(B-2) Sintered Density The sintered density of the dielectric ceramic was measured by an underwater displacement method. The measurement results are shown in Table 1.

(B-3) Dielectric properties; ε and tan δ LCZ meter (manufactured by Yokogawa Hewlett-Packard, 4276A)
The dielectric constant; ε and the dielectric loss tangent; tan δ were measured at 20° C. and IKHz. The measurement results are shown in Table 1.

〔Effect of the invention〕

As shown in the Examples and Comparative Examples, the raw material powder produced by the method of the present invention is sinterable at low temperatures, and the PZT piezoelectric ceramic sintered body obtained by sintering the powder has high density and good electrical properties. Excellent. These effects were obtained by the order of precipitate formation of the constituent components, that is, the selection of precursors and intermediate washing, and the effects became even more pronounced by the combination of the ripening steps.
As described above, according to the present invention, PZ with excellent electrical properties
T-type ceramics can be easily produced, and their industrial value is extremely large.

Patent applicant: Director, Inorganic Materials Research Institute, Science and Technology Agency (430)
Nippon Soda Co., Ltd.

Claims (2)

[Claims] (1) After mixing a zirconium compound aqueous solution with an excess precipitate forming liquid to form a precipitate, a titanium compound aqueous solution is mixed with the precipitate forming liquid in which the precipitate is dispersed to form a composite precipitate,
After washing the obtained composite precipitate, the composite precipitate is again dispersed in an excess precipitate forming liquid, and an aqueous lead compound solution is mixed with the precipitate-dispersed precipitate forming liquid to form a composite precipitate of all the components. A method for producing a low-temperature sinterable PZT-based piezoelectric ceramic powder, which is characterized by calcination at 500 to 1100°C after filtration and washing. (2) The method according to claim (1), in which after each precipitate is formed, the temperature is maintained at 10 to 80°C for ripening.